Disclosed herein, in various embodiments, are stable, high performing nanoparticle compositions suitable for printing, such as by inkjet printing.
Fabrication of electronic circuit elements using liquid deposition techniques is of profound interest as such techniques provide potentially low-cost alternatives to conventional mainstream amorphous silicon technologies for electronic applications such as thin film transistors (TFTs), light-emitting diodes (LEDs), RFID tags, photovoltaics, printed memory, and the like. However, the deposition and/or patterning of functional electrodes, pixel pads, and conductive traces, lines and tracks, which meet the conductivity, processing, morphology, and cost requirements for practical applications, have been a great challenge.
Solution-processable conductors are of great interest for use in such electronic applications. Metal nanoparticle-based inks represent a promising class of materials for printed electronics. However, most metal nanoparticles, such as silver and gold metal nanoparticles, require large molecular weight stabilizers to ensure proper solubility and stability in forming a printing solution. These large molecular weight stabilizers inevitably raise the annealing temperature for the metal nanoparticles above 200° C. in order to burn off the stabilizers, which temperatures are incompatible with most low-cost plastic substrates such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) that the solution may be coated onto and can cause damage thereto.
Furthermore, current metal nanoparticle compositions when deposited on a substrate often result in conductive metal ink lines that are too wide, exhibit a low conductivity, and have a “coffee ring effect.” The current metal ink compositions also have a large surface roughness, which is exhibited by “black dots” appearing within the printed line. Coffee ring effect is referred to herein as when the particles in a given droplet end up along the circumference of the circle having a very thin center where the droplet was deposited on the substrate (i.e. a non-uniform deposition). In a cross-section of the droplet, a bimodal line profile (two peaks) in a surface profile measurement is observed. The deposition of a conductive metal line that exhibits a coffee ring effect and/or that are otherwise too wide may limit the inks use in certain applications.
Jettable compositions would be desirable to enable drop-on-demand deposition and printing with functional features such as electrodes and interconnects for electronic devices.